1/*
2 * Copyright (C) 2013 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.camera.util;
18
19import android.animation.TimeInterpolator;
20
21/**
22 * Interpolator that uses a Bezier derived S shaped curve.
23 *
24 * TODO: Replace usages with ui.motion classes.
25 */
26public class Gusterpolator implements TimeInterpolator {
27    /** An instance of {@link Gusterpolator}. */
28    public static final Gusterpolator INSTANCE = new Gusterpolator();
29
30    /**
31     * To avoid users of this class creating multiple copies needlessly, the constructor is
32     * private.
33     */
34    private Gusterpolator() {}
35
36    /**
37     * Lookup table values.
38     * Generated using a Bezier curve from (0,0) to (1,1) with control points:
39     * P0 (0,0)
40     * P1 (0.4, 0)
41     * P2 (0.2, 1.0)
42     * P3 (1.0, 1.0)
43     *
44     * Values sampled with x at regular intervals between 0 and 1.
45     */
46    private static final float[] VALUES = new float[] {
47            0.0f, 0.0002f, 0.0009f, 0.0019f, 0.0036f, 0.0059f, 0.0086f, 0.0119f, 0.0157f, 0.0209f,
48            0.0257f, 0.0321f, 0.0392f, 0.0469f, 0.0566f, 0.0656f, 0.0768f, 0.0887f, 0.1033f,
49            0.1186f, 0.1349f, 0.1519f, 0.1696f, 0.1928f, 0.2121f, 0.237f, 0.2627f, 0.2892f, 0.3109f,
50            0.3386f, 0.3667f, 0.3952f, 0.4241f, 0.4474f, 0.4766f, 0.5f, 0.5234f, 0.5468f, 0.5701f,
51            0.5933f, 0.6134f, 0.6333f, 0.6531f, 0.6698f, 0.6891f, 0.7054f, 0.7214f, 0.7346f,
52            0.7502f, 0.763f, 0.7756f, 0.7879f, 0.8f, 0.8107f, 0.8212f, 0.8326f, 0.8415f, 0.8503f,
53            0.8588f, 0.8672f, 0.8754f, 0.8833f, 0.8911f, 0.8977f, 0.9041f, 0.9113f, 0.9165f,
54            0.9232f, 0.9281f, 0.9328f, 0.9382f, 0.9434f, 0.9476f, 0.9518f, 0.9557f, 0.9596f,
55            0.9632f, 0.9662f, 0.9695f, 0.9722f, 0.9753f, 0.9777f, 0.9805f, 0.9826f, 0.9847f,
56            0.9866f, 0.9884f, 0.9901f, 0.9917f, 0.9931f, 0.9944f, 0.9955f, 0.9964f, 0.9973f,
57            0.9981f, 0.9986f, 0.9992f, 0.9995f, 0.9998f, 1.0f, 1.0f
58    };
59
60    private static final float STEP_SIZE = 1.0f / (VALUES.length - 1);
61
62    @Override
63    public float getInterpolation(float input) {
64        if (input >= 1.0f) {
65            return 1.0f;
66        }
67
68        if (input <= 0f) {
69            return 0f;
70        }
71
72        int position = Math.min(
73                (int)(input * (VALUES.length - 1)),
74                VALUES.length - 2);
75
76        float quantized = position * STEP_SIZE;
77        float difference = input - quantized;
78        float weight = difference / STEP_SIZE;
79
80        return VALUES[position] + weight * (VALUES[position + 1] - VALUES[position]);
81    }
82}
83